Department of Entomology, Texas A&M University, College Station, TX 77843, United States; Institute for Plant Genomics & Biotechnology, Texas A&M University, College Station, TX 77843, United States.
Department of Biology, Canisius College, Buffalo, NY, United States.
J Insect Physiol. 2020 May-Jun;123:104054. doi: 10.1016/j.jinsphys.2020.104054. Epub 2020 Apr 7.
Sterols are essential membrane components and are critical for many physiological processes in all eukaryotes. Insects and other arthropods are sterol auxotrophs that typically rely on a dietary source of sterols. Herbivorous insects generally obtain sterols from plants and then metabolize them into cholesterol, the dominant sterol in most insects. However, there is significant variation in phytosterol structure, and not all phytosterols are equally suitable for insects. In the current study, we used seven Arabidopsis thaliana lines that display altered sterol profiles due to mutations in the sterol biosynthetic pathway or to overexpression of key enzymes of the pathway, and investigated how plant sterol profiles affected green peach aphid (Myzus persicae) growth and reproduction. We also characterized the sterol profile of aphids reared on these Arabidopsis genotypes. Aphids on two mutant lines (14R/fk and ste1-1) that accumulated biosynthetic sterol intermediates (Δ-sterols, and Δ-sterols, respectively) all showed significantly reduced growth and reproduction. Aphids on SMT2 plants (which have decreased β-sitosterol but increased campesterol) also displayed significantly reduced growth and reproduction. However, aphids on SMT2 plants (which have increased β-sitosterol but decreased campesterol) performed similarly to aphids on wild-type plants. Finally, Arabidopsis plants that had an overproduction of sterols (CD-HMGR) or decreased sterol esters (psat1-2) had no impact on aphid performance. Two noteworthy results come from the aphid sterol profile study. First, β-sitosterol, cholesterol and stigmasterol were recovered in all aphids. Second, we did not detect Δ-sterols in aphids reared on 14R/fk plants. We discuss the implications of our findings, including how aphid sterol content does not appear to reflect plant leaf sterol profiles. We also discuss the potential of modifying plant sterol profiles to control insect herbivore pests, including aphids.
甾醇是膜的必需成分，对所有真核生物的许多生理过程都至关重要。昆虫和其他节肢动物是甾醇营养缺陷型生物，通常依赖饮食中的甾醇来源。植食性昆虫通常从植物中获取甾醇，然后将其代谢为胆固醇，胆固醇是大多数昆虫中主要的甾醇。然而，植物甾醇的结构存在很大差异，并非所有植物甾醇对昆虫都同样适用。在本研究中，我们使用了七种拟南芥（Arabidopsis thaliana）品系，这些品系由于甾醇生物合成途径中的突变或该途径中关键酶的过表达而导致甾醇谱发生改变，研究了植物甾醇谱如何影响绿桃蚜（Myzus persicae）的生长和繁殖。我们还对在这些拟南芥基因型上饲养的蚜虫的甾醇谱进行了表征。在两种突变体品系（14R/fk 和 ste1-1）上饲养的蚜虫，其甾醇生物合成中间体（分别为Δ-甾醇和Δ-甾醇）积累，其生长和繁殖均显著降低。甾醇含量降低而β-谷甾醇含量增加的 SMT2 植株上的蚜虫也表现出明显的生长和繁殖减少。然而，β-谷甾醇含量增加而 campesterol 含量减少的 SMT2 植株上的蚜虫的表现与野生型植株上的蚜虫相似。最后，甾醇过度产生（CD-HMGR）或甾醇酯减少（psat1-2）的拟南芥植株对蚜虫的表现没有影响。蚜虫甾醇谱研究有两个值得注意的结果。首先，β-谷甾醇、胆固醇和豆甾醇均在所有蚜虫中回收。其次，我们在 14R/fk 植株上饲养的蚜虫中未检测到Δ-甾醇。我们讨论了我们研究结果的意义，包括蚜虫甾醇含量似乎并不反映植物叶片甾醇谱的情况。我们还讨论了改变植物甾醇谱以控制昆虫草食性害虫（包括蚜虫）的潜力。
